1. Field of the invention
The present invention relates to a system for use on a load transportation vehicle, having an auxiliary axle with a suspension of the pneumatic type, which system is capable of automatically and accurately distributing the load to be carried by the vehicle between at least one of the main axle, preferably the front one, and the auxiliary axle, whenever the latter is needed.
2. Description of the prior art
Vehicles to which the invention particularly applies are those equipped with retractable auxiliary wheels between the front steering wheels and the rear wheels; the auxiliary retractable wheels being intended to carry a surplus load when brought to ground-engaging position. Both suspensions for the steering wheels and for the auxiliary wheels include inflatable balloons either exclusively or in combination with spring blades.
As is known, it is of prime importance that the steering wheels not be overloaded or underloaded at any time so that the driver may be able constantly to control steering of the vehicle properly. This is particularly so whenever the vehicle carries a surplus load at which time the auxiliary wheels have to be used and the load distributed so that the steering wheels are neither overloaded or underloaded. Apart from difficulties in driving, the driver may be penalized, at a load-measuring station along the road, for having an overloaded axle.
At the present time, it is possible for the vehicle driver to inflate or deflate the suspension balloons manually to try to reach the best possible load distribution between the steering and auxiliary wheels, but this can only be done manually, as aforesaid. There is indeed absolutely no way for him to assess with any accuracy whether or not the load distribution has been done properly except by means of his own experienced perception of the vehicle behaviour as sensed through the steering column. It will be appreciated that such an adjustment is quite subjective and therefore may lead to dangerous situations, not to mention rendering driving more difficult.